Methods of forming void-free layers in openings of semiconductor substrates

ABSTRACT

In a method of manufacturing a floating gate of a non-volatile semiconductor memory, a pattern is formed on a substrate to have an opening that exposes a portion of the substrate. A first preliminary polysilicon layer is formed on the pattern and the exposed portion of the substrate to substantially fill the opening. A first polysilicon layer is formed by partially etching the first preliminary polysilicon layer until a first void formed in the first preliminary polysilicon layer is exposed. A second polysilicon layer is formed on the first polysilicon layer.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 USC § 119 of Korean PatentApplication No. 2004-0043937 filed on Jun. 15, 2004, the disclosure ofwhich is hereby incorporated herein by reference in its entirety as ifset forth fully herein.

FIELD OF THE INVENTION

The present invention relates to methods of manufacturing semiconductordevices. More particularly, the present invention relates to methods offorming layers in openings of semiconductor substrates.

BACKGROUND OF THE INVENTION

Semiconductor memory devices may be divided into volatile semiconductormemory devices, such as a dynamic random access memory (DRAM) devices orstatic random access memory (SRAM) devices, and non-volatilesemiconductor memory devices, such as read only memory (ROM) devices,flash memory devices or electrically erasable and programmable read onlymemory (EEPROM) devices. In a flash memory device, data may beelectrically stored into the flash memory device or read out from theflash memory device using a Fowler-Nordheim tunneling method or achannel hot electron injection method.

A method of manufacturing a non-volatile semiconductor memory devicesuch as the flash memory device is disclosed in U.S. Pat. No. 6,465,293issued to Park et al. As described in the Park et al. Abstract, themethod comprises the steps of forming an oxide film on a semiconductorsubstrate in which a device separation film is formed and thenpatterning the oxide film to expose the semiconductor substrate at aportion in which a floating gate will be formed; sequentially forming atunnel oxide film and a first polysilicon layer on the entire structure,and then flattening the first polysilicon layer until the tunnel oxidefilm is exposed to form a floating gate; etching the tunnel oxide filmand the oxide film in the exposed portion to a given thickness and theforming a dielectric film on the entire structure; sequentially forminga second polysilicon layer, a tungsten silicide layer and a hard maskand then patterning them to form a control gate; and injecting impurityions into the semiconductor substrate at the both sides of the floatinggate to form a junction region.

As the integration density of semiconductor devices continues toincrease, an opening defined by an oxide pattern that partially exposesa semiconductor substrate may have a high aspect ratio. When the openinghas the high aspect ratio, a polysilicon layer filling up the openingmay have a void therein in a process for manufacturing the semiconductordevice.

FIG. 1 is an electron microscopic photograph illustrating a voidgenerated in a polysilicon layer in a conventional method for forming afloating gate.

As shown in FIG. 1, a void 12 generated in a polysilicon layer 10 maynot be removed in a planarization process for forming the floating gate.Thus, a portion of the floating gate around the void 12 may be oxidizedin successive processes, thereby deteriorating electricalcharacteristics of a semiconductor device including the floating gate.

SUMMARY OF THE INVENTION

Some embodiments of the invention provide methods of forming void-freelayers in openings of semiconductor substrates. More specifically, afirst layer is formed in an opening in a semiconductor substrate,wherein the first layer includes a void therein that extends at leastpartially in the opening. As used herein, a “void” means a substantiallyenclosed empty space in a layer. The first layer is etched in theopening to at least expose the void. A second layer is then formed inthe opening on the first layer that has been etched to at least exposethe void. In some embodiments, the first and second layers comprisepolysilicon. In some embodiments, the first and second layers are ofidentical composition. In some embodiments, etching the first layer inthe opening to at least expose the void comprises etching the firstlayer in the opening to eliminate the void.

Moreover, in some embodiments, the first layer is formed by forming afirst layer in and outside the opening in the semiconductor substrate,wherein the first layer includes the void therein that extends at leastpartially in the opening. The first layer is then etched to remove thefirst layer outside the opening, and to at least expose the void.

In other embodiments, the void is a first void, and the second layeralso includes a second void therein that extends at least partially inthe opening. In some embodiments, the second layer may be etched in theopening to at least expose the second void and a third layer is formedin the opening on the second layer that has been etched to at leastexpose the second void.

Embodiments of the present invention as described above may be used tomanufacture any layer in an opening in a semiconductor substrate.Embodiments that will now be described may be used specifically to forma polysilicon layer in an opening in a semiconductor substrate and maybe particularly used in forming self-aligned polysilicon layers forflash memory devices.

More specifically, in some embodiments of the present invention, apattern is formed on a substrate. The pattern has an opening thatexposes a portion of the substrate. A first preliminary polysiliconlayer is formed on the pattern and the exposed portion of the substrateto substantially fill up the opening, except for a first void in thefirst preliminary polysilicon layer. A first polysilicon layer is formedby partially etching the first preliminary polysilicon layer until thefirst void in the first preliminary polysilicon layer is exposed. Thefirst polysilicon layer may be formed in the opening only. Then, asecond polysilicon layer is formed on the first polysilicon layer.

In some embodiments, the first preliminary polysilicon layer may bepartially etched by a wet etching process at a temperature of about 70°C. to about 90° C. using an etching solution that includes ammoniumhydroxide (NH₄OH), hydrogen peroxide (H₂O₂) and deionized water (H₂O) bya molar ratio of about 3 to about 10: about 1: about 60 to about 200.Moreover, in forming the second polysilicon layer, the secondpreliminary polysilicon layer may be formed on the first polysiliconlayer and on the pattern to substantially fill a recess caused by theexposure of the first void, except for a second void in the secondpreliminary polysilicon layer. The second preliminary polysilicon layermay be partially etched to expose the second void in the secondpreliminary polysilicon layer, thereby forming the second polysiliconlayer. A third polysilicon layer may be further formed on the secondpolysilicon layer in some embodiments.

In accordance with yet other embodiments of the present invention, amask pattern is formed on a substrate to have a first opening thatexposes a portion of the substrate. A trench is formed by etching theexposed portion of the substrate using the mask pattern as an etchingmask. An insulation pattern is formed to fill the trench and the firstopening. The mask pattern is removed to form a second opening thatexposes an active region of the substrate defined by the insulationpattern. A preliminary polysilicon layer is formed on the insulationpattern and on the active region to substantially fill the secondopening, except for a void in the preliminary polysilicon layer. A firstpolysilicon layer is formed by partially etching the preliminarypolysilicon layer until the void in the preliminary polysilicon layer isexposed. A second polysilicon layer is formed on the first polysiliconlayer. A floating gate is formed in the second opening by partiallyremoving the second polysilicon layer until the insulation pattern isexposed. A first dielectric layer may be formed on the active region ofthe substrate after removing the mask pattern. The first polysiliconlayer may be formed in the second opening only, and the secondpolysilicon layer may be formed on the insulation pattern and on thefirst polysilicon layer to fill a recess caused by an exposure of thevoid. A second dielectric layer may be formed on the floating gate, andthen a control gate may be formed on the second dielectric layer.

According to some embodiments of the present invention, a floating gateof a non-volatile semiconductor memory device may be formed on asubstrate without formation of voids in the floating gate because atleast one preliminary polysilicon layer is employed for forming thefloating gate and at least one etching process is carried out to atleast partially remove voids in the preliminary polysilicon layer.Therefore, the non-volatile semiconductor memory device may haveimproved electrical characteristics and also throughput of asemiconductor memory device manufacturing process may be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron microscopic photograph illustrating a voidgenerated in a polysilicon layer in a conventional method for forming afloating gate;

FIGS. 2 to 8, 10 and 11 are cross sectional views illustrating methodsof manufacturing semiconductor devices in accordance with exemplaryembodiments of the present invention;

FIG. 9 is an electron microscopic photograph illustrating the firstpolysilicon layer and the second preliminary polysilicon layer in FIG.8; and

FIGS. 12 to 14 are cross sectional views illustrating methods ofmanufacturing semiconductor devices in accordance with other exemplaryembodiments of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly on” another element, there are no intervening elementspresent. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items and may beabbreviated as “/”.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first layer could be termed asecond layer, and, similarly, a second layer could be termed a firstlayer without departing from the teachings of the disclosure.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother elements as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower”, can therefore, encompasses both an orientation of “lower” and“upper,” depending of the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Embodiments of the present invention are described herein with referenceto cross section illustrations that are schematic illustrations ofidealized embodiments of the present invention. As such, variations fromthe shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,embodiments of the present invention should not be construed as limitedto the particular shapes of regions illustrated herein but are toinclude deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described as flatmay, typically, have rough and/or nonlinear features. Moreover, sharpangles that are illustrated, typically, may be rounded. Thus, theregions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the precise shape of a region andare not intended to limit the scope of the present invention.

FIGS. 2 to 8, 10 and 11 are cross sectional views illustrating methodsof manufacturing semiconductor devices in accordance with exemplaryembodiments of the present invention.

FIG. 2 is a cross sectional view illustrating forming mask patterns 106on a substrate 100.

Referring to FIG. 2, a pad oxide layer 102 is formed on a semiconductorsubstrate 100. The semiconductor substrate 100 may include a siliconwafer. The pad oxide layer 102 may be formed on the substrate 100 by athermal oxidation process and/or a chemical vapor deposition (CVD)process.

A mask layer (not shown) is formed on the pad oxide layer 102. The masklayer may include a nitride such as silicon nitride. The mask layer maybe formed using a source gas that includes SiH₂Cl₂, SiH₄ and/or NH₃.Additionally, the mask layer may be formed on the pad oxide layer 102 bya low pressure chemical vapor deposition (LPCVD) process and/or a plasmaenhanced chemical vapor deposition (PECVD) process.

After a photoresist film is formed on the mask layer, the photoresistfilm is exposed and developed to thereby form photoresist patterns 104on the mask layer. The mask patterns 106 are formed on the pad oxidelayer 102 by partially etching the mask layer using the photoresistpatterns 104 as an etching mask. Here, the mask layer may be etched by adry etching process and/or a reactive ion etching process.

After the mask patterns 106 are formed on the pad oxide layer 102, thephotoresist patterns 104 are removed from the mask patterns 106 by anashing process and/or a stripping process.

FIG. 3 is a cross sectional view illustrating forming trenches 108 onthe substrate 100.

As shown in FIG. 3, the pad oxide layer 102 and the substrate 100 arepartially etched using the mask patterns 106 as etching masks to therebyform the trenches 108 on the substrate 100. Here, portions of the padoxide layer 102 and the substrate 100 between the mask patterns 106 areetched to form the trenches 108. The trenches 108 are formed along afirst direction crossing the substrate 100. When the trenches 108 areformed, pad oxide patterns 103 are formed between the mask patterns 106and the substrate 100. Each of the trenches 108 may have a depth ofabout 1,000 Å to about 5,000 Å, and in some embodiments, a depth ofabout 2,300 Å.

Insides of the trenches 108 may be oxidized in order to cure damage tothe trenches 108 caused by the etching process of forming the trenches108. That is, thin oxide layers may be formed on the insides of thetrenches 108, respectively. These thin oxide layers may additionallyprevent generation of leakage currents from the trenches 108. Each ofthe thin oxide layers may have a thickness of about 30 Å.

FIG. 4 is a cross sectional view illustrating forming field insulationpatterns 110 in the trenches 108.

Referring to FIG. 4, an insulation layer (not shown) is formed on thepad oxide patterns 103 to fill up the trenches 108. The insulation layermay be formed using an oxide such as silicon oxide. Namely, theinsulation layer may include undoped silicate glass (USG), 0₃-terraethyl ortho silicate (TEOS) and/or high density plasma-chemical vapordeposition (HDP-CVD) oxide. In some embodiments, the insulation layermay include HDP-CVD oxide formed using a gas mixture of SiH₄, O₂ and/orargon (Ar) as a plasma source.

The insulation layer is partially removed by a chemical mechanicalpolishing (CMP) process, an etch back process or a combination processof the CMP process and the etch back process until the mask patterns 106are exposed. As a result, the field insulation patterns 110 arerespectively formed in the trenches 108 to define active regions 100 aon the substrate 100.

FIG. 5 is a cross sectional view illustrating forming openings 112.

Referring to FIG. 5, the mask patterns 106 and the pad oxide patterns103 are removed from the substrate 100 to thereby form the openings 112that expose portions of the substrate 100. The openings 112 defined bythe insulation patterns 110 may be formed by a wet etching processand/or a dry etching process. For example, the openings 112 are formedby the wet etching process using an etching solution that includesphosphoric acid. When the openings 112 are formed, lower sidewalls ofthe insulation patterns 110 may be slightly etched in the etchingprocess of etching the mask patterns 106 and the pad oxide patterns 103.

Accordingly, FIGS. 2 to 5 illustrate forming an opening in asemiconductor substrate, where the semiconductor substrate includes asilicon wafer, and also can include one or more layers thereon. Thus,the opening may be entirely within the layer(s) 110 on the semiconductorsubstrate 100, as shown in FIG. 5, entirely within the semiconductorsubstrate 100, or may extend from the layer(s) 110 on the semiconductorsubstrate 100 into the semiconductor substrate 100 itself.

FIG. 6 is a cross sectional view illustrating forming a firstpreliminary polysilicon layer 116.

Referring to FIG. 6, a first dielectric layer 114 or a tunnel oxidelayer is formed on the exposed portions of the substrate 100 through theopenings 112. The first dielectric layer 114 may be formed using anoxide such as silicon oxide by a thermal oxidation process and/or a CVDprocess. Alternatively, the first dielectric layer 114 may includesilicon oxide doped with impurities such as fluorine and/or carbon.Furthermore, the first dielectric layer 114 may include a materialhaving a low dielectric constant such as an organic polymer, forexample, polyallylether resin, cyclic fluorine resin, siloxane copolymerresin, polyallyletherfluoride resin, polypentafluorostyrene resin,polytetrafluorostyrene resin, polyimidefluoride resin,polynaphthalenefluoride and/or polycide resin, etc. When the firstdielectric layer 114 includes the organic polymer, the first dielectriclayer 114 may be formed on the exposed portions of the substrate 100 bya plasma enhanced chemical vapor deposition (PECVD) process, an HDP-CVDprocess, a spin coating process and/or an atmospheric pressure chemicalvapor deposition (APCVD) process.

The first preliminary polysilicon layer 116 is formed on the firstdielectric layer 114 to completely cover the insulation patterns 110.Accordingly, the openings 112 are substantially covered with thepreliminary polysilicon layer 116. The first preliminary polysiliconlayer 116 may be formed using an LPCVD process. Impurities are dopedinto the first preliminary polysilicon layer 116 by an ion implantationprocess, a diffusion process, an in-situ doping process and/or otherprocess.

When the first preliminary polysilicon layer 116 is formed to fill upthe openings 112, voids 118 are formed in portions of the firstpreliminary polysilicon layer 116 between the insulation patterns 110.These voids 118 may be more likely formed in the first preliminarypolysilicon layer 116 when the openings 112 have increased aspectratios. That is, as the aspect ratios of the openings 112 increase, thedimensions of the voids 118 may increase and also the formationprobability of the voids 118 may grow larger. The voids 118 may degradeelectrical characteristics of a floating gate 125 (see FIG. 10)subsequently formed. Alternatively, FIG. 6 illustrates forming a firstlayer 116 in an opening 112 in the semiconductor substrate 100, thefirst layer 116 including a void 118 therein that extends at leastpartially in the opening 112, according to various embodiments of thepresent invention.

FIG. 7 is a cross sectional view illustrating forming a firstpolysilicon layer 120.

Referring to FIG. 7, an upper portion of the first preliminarypolysilicon layer 116 is removed until the voids 118 are exposed tothereby form the first polysilicon layer 120 on the first dielectriclayer 114. When the first preliminary polysilicon layer 116 is partiallyremoved until the voids 118 are exposed, upper portions of theinsulation patterns 110 are simultaneously exposed. Thus, the firstpreliminary polysilicon layer 116 remains between the insulationpatterns 110. Namely, lower portions of the openings 112 are filled withthe remaining first preliminary polysilicon layer 116 that correspondsto the first polysilicon layer 120. Since the first polysilicon layer120 is formed on the first dielectric layer 114 between the insulationpatterns 110, the first polysilicon layer 120 is self-aligned relativeto the insulation patterns 110. In particular, the first polysiliconlayer 120 exists on the first dielectric layer 114 only. An upper faceof the first polysilicon layer 120 is substantially lower than faces ofthe insulation patterns 110. Hence, recesses 122 are formed on the firstpolysilicon layer 120. The recesses 122 are defined by the sidewalls ofthe insulation patterns 110 and the upper face of the first polysiliconlayer 120. Alternatively, FIG. 7 illustrates etching the first layer 116in the opening 112 to at least expose the void 118. Etching may takeplace to only expose the void 118 but not eliminate the void 118, or mayproceed to eliminate the void 118, as shown in FIG. 7.

The upper portion of the first preliminary polysilicon layer 116 may beremoved by a wet etching process. If the first preliminary polysiliconlayer 116 is partially etched by a dry etching using a plasma, the firstdielectric layer 114 may be damaged in the etching process. In the wetetching process of partially etching the first preliminary polysiliconlayer 116, an etching solution having a high etching selectivityrelative to oxide may be used. The etching solution may include ammoniumhydroxide (NH₄OH), hydrogen peroxide (H₂O₂) and/or deionized water (H₂O)so that the upper portion of the first preliminary polysilicon layer 116is advantageously etched without damage to the insulation patterns 110.For example, the etching solution may include a standard cleaning (SC) 1solution and/or a new standard cleaning (NSC) 1 solution. The NSC 1solution includes ammonium hydroxide (NH₄OH), hydrogen peroxide (H₂O₂)and deionized water (H₂O) by a molar ratio of about 3 to about 10: about1: about 60 to about 200. The NSC 1 solution may include ammoniumhydroxide, hydrogen peroxide and deionized water by a molar ratio ofabout 4: about 1: about 95. The wet etching process may be carried outat a temperature of about 70° C. to about 90° C., and in someembodiments, at a temperature of about 80° C.

When the first polysilicon layer 120 is formed by the wet etchingprocess at the temperature of about 80° C. using the NSC 1 solution thatincludes ammonium hydroxide, hydrogen peroxide and deionized water by amolar ratio of about 4: about 1: about 95, the etching solution has anetching selectivity of about 12.5: about 1 between polysilicon andoxide. Particularly, an etching rate of the first preliminarypolysilicon layer 116 is about 31.5 Å/minute, whereas an etching rate ofthe insulation patterns 110 is about 2.5 Å/minute.

In some embodiments of the present invention, the etching solution hasan etching selectivity of about 5.5: about 1 between polysilicon andoxide when the first preliminary polysilicon layer 116 is partiallyetched by the wet etching process at the temperature of about 70° C.using the SC 1 solution that includes ammonium hydroxide, hydrogenperoxide and deionized water by a molar ratio of about 1: about 4: about20. That is, an etching rate of the first preliminary polysilicon layer116 is about 8 Å/minute, whereas an etching rate of the insulationpatterns 110 is about 1.4 Å/minute. For example, the wet etching processmay be performed for about 10 to about 30 minutes when the firstpreliminary polysilicon layer 116 has a thickness of about 400 to about600 Å.

FIG. 8 is a cross sectional view illustrating forming a secondpreliminary polysilicon layer 124, and FIG. 9 is an electron microscopicphotograph illustrating the first polysilicon layer 120 and the secondpreliminary polysilicon layer 124 in FIG. 8.

Referring to FIGS. 8 and 9, the second preliminary polysilicon layer 124is formed on the first polysilicon layer 120 and the insulation patterns110 to fill up the recesses 122. The second preliminary polysiliconlayer 124 may be formed by a process substantially identical to that ofthe first preliminary polysilicon layer 116. That is, the secondpreliminary polysilicon layer 124 may be formed by an LPCVD process, andimpurities may be doped into the second preliminary polysilicon layer124 by an ion implantation process, a diffusion process, an in-situdoping process and/or other processes.

As described above, the voids 118 in the first preliminary polysiliconlayer 116 are removed through the wet etching process in the steps forforming the self-aligned first polysilicon layer 120 and the secondpreliminary polysilicon layer 124. As a result, the voids 118 are notformed between the first polysilicon layer 120 and the secondpreliminary polysilicon layer 124 as shown in FIG. 9. Thus, FIGS. 8 and9 illustrate forming a second layer 124 in the opening on the firstlayer 120 that has been etched to at least expose the void 118.

FIG. 10 is a cross sectional view illustrating forming the floating gate125.

Referring to FIG. 10, an upper portion of the second preliminarypolysilicon layer 124 is removed by a planarization process until theinsulation patterns 110 are exposed, thereby forming the floating gate126 that fills the recess 122. The floating gate 126 may be formed by aCMP process, an etch back process or a combination process of the CMPprocess and the etch back process. When the second preliminarypolysilicon layer 124 is partially removed, a second polysilicon layer128 is formed on the first polysilicon layer 120. The floating gate 126includes the first polysilicon layer 120 and the second polysiliconlayer 128 successively formed on the first dielectric layer 114.

FIG. 11 is a cross sectional view illustrating forming a seconddielectric layer 130 and a control gate.

Referring to FIG. 11, upper portions of the insulation patterns 110 areremoved to predetermined depths by an etching process such as anisotropic etching process and/or an anisotropic etching process. Upperfaces of the etched insulation patterns 110 are substantially higherthan that of the first dielectric layer 114 so that the first dielectriclayer 114 may not be damaged in the etching process.

The second dielectric layer 130 is formed on the etched insulationpatterns 110 and the floating gate 126. The second dielectric layer 130may be formed using a material that has a high dielectric constant suchas yttrium oxide (Y₂O₃), hafnium oxide (HfO₂), zirconium oxide (ZrO₂),niobium oxide (Nb₂O₅), barium titanate (BaTiO₃), strontium titanate(SrTiO₃) and/or other materials. Alternatively, the second dielectriclayer 130 may have an ONO structure in which an oxide film, a nitridefilm and an oxide film are successively formed. The second dielectriclayer 130 may be formed using LPCVD process, an atomic layer deposition(ALD) process, a CVD process and/or other process.

A first conductive layer 132 and a second conductive layer 134 aresequentially formed on the second dielectric layer 130 to thereby formthe control gate layer 136 on the second dielectric layer 130. The firstconductive layer 132 may include polysilicon doped with impurities, andthe second conductive layer 134 may include a metal silicide. Forexample, the second conductive layer 134 may include tungsten silicide(WSi_(x)), titanium silicide (TiSi_(x)), cobalt silicide (CoSi_(x))and/or tantalum silicide (TaSi_(x)).

The control gate layer 136 is partially etched to form the control gate(not shown) on the second dielectric layer 130. The control gate extendsalong a second direction substantially perpendicular to the firstdirection. When the second dielectric layer 130, the floating gate 126and the first dielectric layer 114 are sequentially patterned, a gatestructure of a non-volatile semiconductor memory device is formed on thesubstrate 100. Source/drain regions (not shown) may then be formed inthe active region 100 a extending in the first direction by implantingimpurities into portions of the active region 100 a, thereby completingthe non-volatile semiconductor memory devices, such as a flash memorydevice.

FIGS. 12 to 14 are cross sectional views illustrating methods ofmanufacturing semiconductor devices in accordance with other exemplaryembodiments of the present invention.

FIG. 12 is a cross sectional view illustrating forming a secondpreliminary polysilicon layer 224.

Referring to FIG. 12, after active regions 200 a are defined on asemiconductor substrate 200, insulation patterns 210 are formed on thesubstrate 200 to expose portions of the active regions 200 a. That is,portions of the substrate 200 are exposed by openings 212 formed betweenthe insulation patterns 210. Here, each of the openings 212 may have anaspect ratio substantially higher than that of the opening 112 shown inFIG. 5.

A first dielectric layer 214 is formed on the exposed portions of thesubstrate 200. A first preliminary polysilicon layer (not shown)including first voids therein is formed on the first dielectric layer214 and the insulation patterns 210 to fill the openings 212. The firstpreliminary polysilicon layer is partially removed until the first voidsare exposed so that a first polysilicon layer 220 is formed on the firstdielectric layer 214. When the first voids are exposed in accordancewith formation of the first polysilicon layer 220, first recesses aregenerated due to the exposed first voids. Each of the first recesses isdefined by a sidewall of the insulation pattern 210 and the firstpolysilicon layer 220 as described above.

The second preliminary polysilicon layer 224 is formed on the firstpolysilicon layer 220 to substantially cover the insulation patterns210. The second preliminary polysilicon layer 224 completely fills thefirst recesses. However, when the second preliminary polysilicon layer224 is formed, second voids 225 may be formed at portions of the secondpreliminary polysilicon layer 224 defined by the first recesses. Thatis, the second voids 225 may be formed at portions of the secondpreliminary polysilicon layer 224 where the first recesses arepositioned because the second preliminary polysilicon layer 224 isformed to fill up the first recesses. Alternatively, FIG. 12 illustratesthat the second layer 224 includes a second void 225 therein thatextends at least partially in the opening 212.

FIG. 13 is a cross sectional view illustrating forming a secondpolysilicon layer 228.

Referring to FIG. 13, an upper portion of the second preliminarypolysilicon layer 224 is removed by a wet etching process until thesecond voids 225 are exposed, thereby forming the second polysiliconlayer 228 on the first polysilicon layer 220. The second preliminarypolysilicon layer 224 may be partially etched using an etching solutionincluding an SC 1 solution and/or an NSC 1 solution. When the secondpolysilicon layer 228 is formed on the first polysilicon layer 220,second recesses 230 are generated between the insulation patterns 210due to the second voids 225. Alternatively, FIG. 13 illustrates etchingthe second layer 224 in the opening 212 to at least expose the secondvoid 225 and, as shown in FIG. 13, to eliminate the second void 225.

FIG. 14 is a cross sectional view illustrating forming a floating gate234.

Referring to FIG. 14, a third preliminary polysilicon layer (not shown)is formed on the second polysilicon layer 228 and the insulationpatterns 210 to fill the second recesses 230. The third preliminarypolysilicon layer is partially etched until the insulation patterns 210are exposed so that a third polysilicon layer 232 is formed on thesecond polysilicon layer 228. Accordingly, the floating gate 234including the first to the third polysilicon layers 220, 228 and 232 isformed on the substrate 200. This floating gate 234 may beadvantageously employed when the floating gate 234 filling up theopening 212 between the insulation patterns 210 is formed on the activeregion 200 a of the substrate 200. Namely, the floating gate 234 may beformed on the substrate 200 without formation of a void therein althoughthe opening 212 has an increased aspect ratio.

A second dielectric layer (not shown) and a control gate (not shown) aresequentially formed on the floating gate 234 so that a non-volatilesemiconductor memory device is formed on the substrate 200.

According to some embodiments of the present invention, a floating gateof a non-volatile semiconductor memory device may be formed on asubstrate without formation of voids in the floating gate because atleast one preliminary polysilicon layer is employed for forming thefloating gate and at least one etching process is carried out to atleast partially remove voids in the preliminary polysilicon layer.Therefore, the non-volatile semiconductor memory device may haveimproved electrical characteristics and also throughput of asemiconductor memory device manufacturing process may be enhanced.Moreover, embodiments of the invention may be used with semiconductordevices other than non-volatile semiconductor memory devices, and may beused to form void-free layers other than polysilicon.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

1. A method of manufacturing a semiconductor device comprising: forminga pattern on a substrate, the pattern having an opening that exposes aportion of the substrate; forming a first preliminary polysilicon layeron the pattern and on the exposed portion of the substrate tosubstantially fill the opening, except for a first void in the firstpreliminary polysilicon layer; forming a first polysilicon layer bypartially etching the first preliminary polysilicon layer until thefirst void in the first preliminary polysilicon layer is exposed; andforming a second polysilicon layer on the first polysilicon layer. 2.The method of claim 1, wherein the first preliminary polysilicon layeris partially etched by a wet etching process.
 3. The method of claim 2,wherein the wet etching process is performed using an etching solutionthat includes ammonium hydroxide (NH₄OH), hydrogen peroxide (H₂O₂) anddeionized water (H₂O).
 4. The method of claim 3, wherein a molar ratioof ammonium hydroxide, hydrogen peroxide and deionized water is in arange of about 3 to about 10: about 1: about 60 to about
 200. 5. Themethod of claim 4, the molar ratio of ammonium hydroxide, hydrogenperoxide and deionized water is about 4: about 1: about
 95. 6. Themethod of claim 2, wherein the wet etching process is carried out at atemperature of about 70° C. to about 90° C.
 7. The method of claim 1,wherein the first polysilicon layer is formed in the opening only. 8.The method of claim 7, wherein forming the second polysilicon layercomprises: forming a second preliminary polysilicon layer on the firstpolysilicon layer and on the pattern to substantially fill a recesscaused by an exposure of the first void, except for a second void in thesecond preliminary polysilicon layer; and partially etching the secondpreliminary polysilicon layer to expose the second void in the secondpreliminary polysilicon layer.
 9. The method of claim 8, furthercomprising forming a third polysilicon layer on the second polysiliconlayer.
 10. The method of claim 1, further comprising removing a portionof the second polysilicon layer to expose the pattern.
 11. A method ofmanufacturing a semiconductor device comprising: forming a mask patternon a substrate, the mask pattern having a first opening that exposes aportion of the substrate; forming a trench by etching the exposedportion of the substrate using the mask pattern as an etching mask;forming an insulation pattern filling the trench and the first opening;removing the mask pattern to form a second opening that exposes anactive region of the substrate defined by the insulation pattern;forming a preliminary polysilicon layer on the insulation pattern and onthe active region to substantially fill the second opening, except for avoid in the preliminary polysilicon layer; forming a first polysiliconlayer by partially etching the preliminary polysilicon layer until thevoid in the preliminary polysilicon layer is exposed; forming a secondpolysilicon layer on the first polysilicon layer; and forming a floatinggate in the second opening by partially removing the second polysiliconlayer until the insulation pattern is exposed.
 12. The method of claim11, further comprising forming a first dielectric layer on the activeregion of the substrate after removing the mask pattern.
 13. The methodof claim 11, wherein the first polysilicon layer is formed by a wetetching process.
 14. The method of claim 11, wherein the wet etchingprocess is performed using an etching solution that includes ammoniumhydroxide, hydrogen peroxide and deionized water by a molar ratio ofabout 3 to about 10: about 1: about 60 to about
 200. 15. The method ofclaim 14, wherein the molar ratio of ammonium hydroxide, hydrogenperoxide and deionized water is about 4: about 1: about
 95. 16. Themethod of claim 13, wherein the wet etching process is carried out at atemperature of about 70° C. to about 90° C.
 17. The method of claim 11,wherein the first polysilicon layer is formed in the second openingonly, and the second polysilicon layer is formed on the insulationpattern and on the first polysilicon layer to substantially fill arecess caused by an exposure of the void.
 18. The method of claim 11,further comprising removing an upper portion of the insulation patternafter forming the floating gate.
 19. The method of claim 11, furthercomprising forming a second dielectric layer on the floating gate, andforming a control gate on the second dielectric layer.
 20. A method ofmanufacturing a semiconductor device comprising: forming a first layeron a bottom and sidewalls of an opening that is on an active region of asemiconductor device substrate, the first layer including a void thereinthat is enclosed by the first layer and extends at least partially inthe opening that is on the active region; etching the first layer in theopening to at least open the void; and forming a second layer in thevoid in the opening on the first layer to thereby fill the void and theopening.
 21. The method of claim 20, wherein the first and second layerscomprise polysilicon.
 22. The method of claim 20, wherein the first andsecond layers are of identical composition.
 23. The method of claim 20,wherein forming a first layer comprises forming a first layer in andoutside the opening in the semiconductor device substrate, the firstlayer including the void therein that extends at least partially in theopening; and wherein etching the first layer in the opening to at leastexpose the void comprises etching the first layer to remove the firstlayer outside the opening and to at least expose the void.
 24. Themethod of claim 20, wherein the void is a first void and wherein thesecond layer includes a second void therein that extends at leastpartially in the opening, the method further comprising: etching thesecond layer in the opening to at least expose the second void; andforming a third layer in the opening on the second layer that has beenetched to at least expose the second void.
 25. The method of claim 20,wherein etching the first layer in the opening to at least expose thevoid comprises etching the first layer in the opening to eliminate thevoid.